1. Field of the Invention
The invention pertains to the field of chains. More particularly, the invention pertains to a chain and sprocket assembly including a sprocket contact ring and link plates having a leading corner randomized with link plates having a different profile.
2. Description of Related Art
For roller, bush, and inverted tooth chains, noise reduction in a chain and sprocket assembly has been achieved in two separate, unrelated ways in the prior art. In the first way, chordal action, also called the polygon effect, is reduced by creating an additional surface to contact the chain. The polygon effect leads to undesirable oscillations and vibrations, which increase the operational noise of a system. The additional contact surface with the chain may have the added advantage of reducing the volume of operational noise by reducing the impact force between the chain and the teeth of the sprocket. These chain and sprocket assemblies reduce noise arising from chordal action, but they have an objectionable whine noise caused by the regular timing of impact between the chain and the sprocket.
Early incorporation of an additional contact surface reduced friction and wear on the chain, rather than operating noise. The additional contact surface in U.S. Pat. No. 689,764 MECHANISM FOR TRANSMITTING POWER AND MOTION, issued Dec. 24, 1901 to Titus et al., minimizes the friction between the chain and the sprocket. The additional contact surfaces in U.S. Pat. No. 799,074, DRIVE CHAIN, issued Sep. 12, 1905 to Morse, reduce wear on the sprocket teeth and the chain rollers.
In U.S. Pat. No. 1,953,388, TRUSS CHAIN, issued Apr. 3, 1934 to Bettin, the chain has trusses to reduce chordal action.
In U.S. Pat. No. 2,199,292, HEAVY DUTY DRIVE CHAIN, issued Apr. 30, 1940 to Pierce, the chain has teeth, in addition to rollers, to provide a second contact means with a sprocket and to reduce chordal action.
In U.S. Pat. No. 2,489,039, CHAIN AND SPROCKET ASSEMBLY, issued Nov. 22, 1949 to Law, for each roller, the chain has a finger, which interacts with a complementary surface between the sprockets to reduce chordal action.
In U.S. Pat. No. 3,597,985, FLEXIBLE POWER TRANSMISSION DRIVE, issued Aug. 10, 1971 to Jeffrey, the sprocket and cooperating chain, shown as an inverted tooth chain, have a mismatched pitch and are provided with complementary engaging surfaces. The sprocket has a shoulder support surface or contact ring. This provides a smooth transitional engagement between the chain and the sprocket and causes the chain to move with the sprocket along a constant sprocket-pitch radius. The guide links have a transitional surface with a radius equal to the distance between the most adjacent pin of the chain and the band support surface at a point tangent to the transitional surface. The transitional surface of the guide links provides a constant radius of engagement between the guide links and the sprocket shoulder support surface.
In WO 03/093700, CHAIN TRANSMISSION AND CHAIN, published Nov. 13, 2003 by Korse et al., the chain is designed to counteract the polygon effect. The chain transmission includes support means for guiding the chain links such that a pivot axis is always at a constant speed when the wheel is rotating at a constant speed. The support means includes a support, which rotates with the wheel. Support surfaces are arranged on the links. The distance between the axis of rotation and the pivot axis is variable.
In the second method of noise reduction, randomization of some aspect of the chain and sprocket assembly is implemented to reduce operational noise. Roller, bush, and inverted tooth chain systems typically exhibit an objectionable whine noise caused by the regular timing of impact, as the individual chain pitches engage the sprocket. Randomization of the chain pitch and of the material of the sprocket-contacting part of the chain is known in the prior art. Randomization modifications do not reduce the noise arising from chordal action, and randomization of the link plate profile is not present in the prior art.
In U.S. Pat. No. 5,192,252, ROLLER CHAIN WITH RANDOMIZED PITCH, issued Mar. 9, 1993 to Skurka et al., the roller chain is provided with sets of links constructed of unequal pitch in order to alter the pattern of contacts between the chain and the sprocket and the resulting noise spectrum. The varying pitch lengths through the chain are achieved by varying the length of either the inside links or the outside links. Alternatively, the sizes and configurations of the rollers are varied. Configurations can include circular, elliptical, or triangular rollers. The pattern of variation of the pitch of the links is randomized throughout the chain.
In U.S. Pat. No. 5,226,856, ROLLER CHAIN CONSTRUCTED WITH NYLON ROLLERS, issued Jul. 13, 1993 to Iacchetta et al., the roller chain is provided with links having some rollers made of nylon. The rollers are arranged with conventional metallic rollers in patterns along the length of a single-strand or double-strand roller chain. The nylon is poly(tetramethylene adipamide). The nylon rollers are placed randomly throughout the chain or in a prescribed random pattern in an effort to modify the noise spectrum.
There is a need in the art for a chain and a chain and sprocket assembly, which reduces operational noise by reducing chordal action and by reducing the regular timing of impact between the chain and the sprocket.